1. The Field of the Invention
The present invention relates generally to communications cards such as PCMCIA-architecture style modem or network cards. More specifically the present invention relates to compensating for heat build-up or temperature changes therein.
2. The Relevant Technology
As computer housings have downsized, internal spatial restrictions have required the establishment of standards for the internal accessories of the computer. One set of standards applicable to memory cards has been developed by the Personal Computer Memory Card International Association (PCMCIA). This organization is comprised of hundreds of manufacturers of memory cards and related peripheral equipment. By convention, the PCMCIA has determined that the spatial standard for all memory cards used in down-sized computers should be restricted to a rectangular space approximately 55 mm in width, 85 mm in length, and either 3.3, 5 or 10.5 mm in depth.
To assure themselves of compatibility and spatial conformity with computers utilizing the PCMCIA standards, internal modem manufacturers have adopted these same spatial standards for their down-sized communications cards. Other communications cards complying with the PCMCIA standards include, but are not limited to, various network cards for use in a LAN or equivalents thereof.
No matter which style of communications card is used, because the size constraints imposed by the PCMCIA standard are so confined, heat has adversely been observed as building-up within the structure of the communications card. Where heretofore this problem was essentially non-existent because of adequate forced-air coolers and large, open spaces available for dissipating heat away from communications cards, this problem has become quite an industry-wide nuisance.
However, to compensate for this heat, many communications cards are configured with variable components dynamically adjusted according to temperature. For example, in a modem communications card, a digital signal processor (DSP) changes various filter coefficients according to line conditions and a measured temperature. In turn, this causes a corresponding change in modem gain. Although effective, modem communications cards experience numerous such changes because they typically require about a 10-15 minute warm-up period before a steady state temperature is achieved.
Detrimentally, adjustments of these components necessitate time-consuming retraining sequences and adaptive filtering to establish various line parameters, such as gain and equalization, between communicating modems. Moreover, it is even possible that during such retraining sequences the net character transmission throughput between the modems can be completely stopped.
Other proposed solutions for overcoming the adverse effects of heat build-up include various hardware implementations. With hardware, however, excessive board space is consumed in an already space-critical environment. Hardware also increases manufacturing costs in labor and component expense. Numerous required retraining sequences have also been reported with these devices.
Accordingly, it would be an advance to provide temperature compensation for communications cards while minimizing retraining sequences during periods of temperature change, especially heat build-up, within the communications card.